The Immortal Life of Henrietta Lacks proved one thing: Oprah Winfrey does indeed get nervous. The iconic talk show host and Oscar-nominated actress stepped into the role of Deborah Lacks, the daughter of Henrietta Lacks, the woman whose cells were used to change the way cancer is treated, for the HBO movie, but it wasn't without hesitation.

"I wasn't quite sure about this role," Winfrey told E! News at the premiere of her HBO movie. "I allowed myself to sort of give myself over to the director George Wolfe and as a result of that I think we have a really fine film. But yeah, I was intimidated."

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Winfrey said part of the hesitation came from her limited acting experience and the range required to play the character. "I've done five movies in my life," she said. "So my repertoire is very small. Every time I'm on stage I just feel like everybody here knows more than I do, so you have to then hand yourself over to somebody who knows what they're doing, so that's what I did."

And it sounds like that worked.

"It's Emmy time," Winfrey's costar Courtney B. Vance told us about her performance. "She's right up there with all the best of them. It's her time."

Winfrey has been attached to the project since 2010 when she signed on to produce it, but it took time to sway her to the acting side. "I wanted it to happen because Deborah wanted it to happen," Rebecca Skloot, the author of the book the movie is based on told us. "For years Deborah Lacks said, ‘There's going to be a movie. Oprah's going to play me, it's going to be amazing.'"

The Immortal Life of Henrietta Lacks airs Saturday, April 22 at 8 p.m. on HBO.